raypsi wrote:
Hey Gary,

Rocks aren't cheap he http://www.icmfg.com/thruhole_crystals.html
Maybe in 9 land they pave the streets with gold.
Personally I'd go with a programmable divider or PLL.

Maybe you like retro, then I'd get some old rocks the ones
you can take apart and grind them down to git's the freq's you need.
I recall grinding some of these to get them into the novice band back
40 yrs ago.
And putting a pencil mark on the quartz to get them to go down in
frequency.
FT243 style can be found here maybe still: http://www.af4k.com/crystals.htm


73 OM

n8zu

On Sep 2, 4:12 pm, Gary@ removenospamandputkf9cm.com wrote:
I am looking for some Heterodyne conversion crystals for a receiver I am
making.
The frequencies a 5 MHz, 7 MHz, 10.5 MHz, 13.5 MHz, 17.5 MHz and 21.5
MHz.
The variable mixing frequency will be from 3 to 3.5 MHz. I would prefer all
the same type holder.

TNX de Gary, KF9CM

You can use the same grinding powder that ATM's (amateur Telescope
makers) use to grind mirrors for grinding crystals. You want the fine
stuff #400 or finer. www.gotgrit.com has this stuff cheap.
Grind the crystal against a piece of scrap plate glass. I've had mixed
results, I've moved a few rocks a few hundred khz and I've also killed
some trying to move them just a few hundred hz.

Only grind ONE side of the rock, put a pencil mark on the other so you
don't mix this up. Wash the crystal well after each grinding session
and only handle it by the edges, you don't want your finger sweat or
oils getting on the crystal. Grinding motion should be a figure 8, use
light pressure and don't push down on the middle of the crystal, handle
by the edges while grinding.

If you do kill the crystal, you might be able to get it to start again
by light grinding using a different motion. Also try holding the
crystal vertical and grind the edges slightly. Measure the thickness
(carefully!) with a micrometer all around. If you ground a 'wedge'
shape into the rock this will also kill and and the cure is to regrind
putting more pressure on the fatter end.

I have quite a few useless FT243 rocks in the junk box, one of these
days I'll probably try moving a few of them to a more useful frequency.

BTW some of those 'useless' frequency rocks do multiply out into some
ham bands.

A few examples from my junk box:
4845khz - 29070khz (10 meters)
6050khz - 18150khz (17 meters)
6025khz - 18075khz (17 meters)
4785khz - 28710hkz (10 meters)
5300khz - 21200hkz (15 meters)